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In Reply to: RE: Is there any real benifit sonically between class A, AB etc... posted by airtime on June 26, 2016 at 07:53:14
You can run class A single-ended or push-pull whether tube or transistor.
So there is a lot of ground to cover here.
But to your question- 'yes' is the simple answer, and comes out of keeping distortion as low as possible.
The human ear converts most forms of distortion into tonality, and in addition has a tipping point where the tonality due to distortion can be favored over actual frequency response errors.
So keeping distortion down is pretty important if you want to have transparency, as distortion will obscure transparency due to the ear's masking principle.
You can suppress distortion by adding loop negative feedback, but its been well-known for the last 60 years that a price is paid for doing so! This involves the addition of higher ordered harmonics and IM distortion that did not exist in the amp otherwise. Of course they are at low levels, but the ear is much more sensitive to higher ordered harmonic distortion than even the best test equipment- it converts the higher ordered harmonic distortion into brightness and hardness.
This is why two amps can have flat frequency response but one might sound bright while the other does not.
Class A operation is one tool in the designer's tool box to help keep distortion down. In doing so, it becomes possible to build an amplifier that is more relaxed and more transparent. Of course there are any number of ways of mucking this up so that the class of operation becomes irrelevant. Much depends on the design!
A lot also depends on your goals. If the best reproduction is your goal then class A will be a part of the equation. If low heat is your goal then class D might be preferable, but it will not be the ultimate in reproduction although it might be quite good. So there is a lot to consider!
Follow Ups:
My opinion on this issue continues to evolve, as time goes forward and becoming more exposed to newer gear available.My current speakers are ATC-SCM19's (with outboard crossovers), along with sub-woofers. I've tried them with many different amp setups, from class A SS mono-blocks, to various class AB SS pre-amps and power amp combos, and high powered tube setups. Each setup has it's own strengths and shortfalls. Based on the aforementioned gear, the tube amps provided the most enjoyment overall with these speakers. The tube gear with the ATC's really brings out many of the best traits of the speaker playback.
About six months ago, auditioned a pair of Class D mono-blocks and the matching pre-amp (Primare A32 preamp and A34.2 power amps). At the same time, picked up a Benchmark DAC-2. I had never been enamored with class D amps overall, but I have to admit, this combination with the ATC/Sub combo is outstanding. Totally changed my previous outlook on class D amps. The difference was VERY noticeable with all types of music, but especially noticeable with complex symphonic music. Dynamic contrasts, ability to hear low level detail cleanly is remarkable. Easily the closest I've been able to come to replicate a live performance. This is extremely difficult to achieve with classical symphonic music, but this setup at least comes somewhat close.
There are a couple of items at work here. One of them is the fact that the ATC speakers need lots of power to sound there best. At 550 watts, clipping is not an issue. I have become a big believer in having lots of power on hand to avoid distortion/clipping. There was article posted some years ago that Bob Carver measured how much power it took to reproduce the sound of scissors, and it took some astronomical amount of power to play it back cleanly.
Another item is the fact that this version of class D (UFPD) sounds very good overall, and gets out of the way to allow the system to reproduce the music. If one just listened to the playback without knowing what the gear was, one would not pick up on the fact that the power amps are class D.
Lastly, there is a synergy with this combo that the sum sounds even better than the parts. The Benchmark DAC-2 is easily one of the best DAC's I've ever heard, and makes the playback sound that much better.
In summary, I think the amp needs to have good synergy with the speakers, regardless of design class.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
Edits: 06/28/16
Its something I've harped on for many years, as you might expect an OTL manufacturer to do :)
Way back in 1974, John Meyer (www.meyersound.com) was working on a high quality high output loudspeaker. In one of our sessions where he'd talk to me about speaker design, we got into speaker/amp matching. He said, and I quote: "It's a SYSTEM!". Truer words were never spoke.
:)
he moved there so he could stay with his girlfriend. He's been with Meyersound for the last 18 years.
This is not *effectively true* unless the amp is able to drive the speakers cleanly. Right?
-
I guess this brings us back to the major issue: Amp/speaker synergy. Every amp manufacturer should provide a list of recommended speakers.
...or the other way - call your speaker manufacturer for a list of recommended amplifiers.
Not practical. Speaker manufacturers just quote power ratings required and are not concerned with different class of amps.IMO You can not beat a well designed class AB amplifier as I have already posted for reliability sonics & cost.
class AB amplifier as I have already posted for reliability sonics & cost
Cost is all over the place...even for Class AB transistor amps (like D'Agostino Momentum for example or darTZeel) so I really think you cannot generalize this point.
Sonicswise, they are also all over the map...from wretched to ok but nothing special.
Cab, From wretched to OK .... LOL ,
I'm sure the same can be said for any genre of amplifiers , many tooby sound Meh to me, only SET's hold corn.
True, many tube amps sound MEH...even some SETs ;-).
You might like some push/pull triode amps though.
Having a GM70 SET built , similar setup to the Lamm ....
Sounds good. What are you using as a driver ? Interstage transformer? What for an output transformer? Silver wire wound? Single output tube or PSE?
I thought your speakers were not really SET friendly? Did you get some horns?
Speakers are similar to Scinnies load wise , but hybrid in the bass, it's a 4 tower setup , pure 2 way ribbon down to 240hz. I'm looking into doing a horn for the first time in 38 yrs something similar to DDK's but smaller in scale.
Amp will be single tube (true SET) trannies were going to be silver via AN, but they would not do a 2 ohm tap , so I'm sourcing from another.
Regards ...
You're gonna have to 'splain to me what "Scinnies" are.
:)
Living in Audio Sin ..... :)
The way that Duke LeJeune of Audiokinesis speakers has tried and highly recommends Ralph's Atma-Sphere OTL amplifiers...
Edits: 06/28/16
"Every amp manufacturer should provide a list of recommended speakers."
I won't argue with that.
If the user is uneducated and doesn't possess the knowledge to determine (for himself) what loads are appropriate and which one's aren't (for a particular amp circuit) then the list would be imperative.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
And, of course, the most helpful list would include speakers that have been evaluated for sound quality as well as electrical compatibility!
The thread post asked about the class of operation.
Asking about speaker compatibility is another matter altogether and one unrelated to class of operation!
However in general, if high fidelity reproduction is your goal, it is to your advantage to look for a speaker that has a higher impedance, regardless of the technology of amplifier (class D solid state or 300b SET).
The reason is that distortion is always lower driving a higher impedance. This can be seen in the specs of all amplifiers made. It is also audible since the ear converts such distortion into tonality. It is true that the difference might look slight on paper, but the ear does not care about the paper and simply hears the difference, and that will be that it will sound less detailed and harsher when driving a lower impedance or more complex load.
Its one thing to know that an amplifier can indeed drive such loads, but that is not the same as that same amplifier sounding its best!
Now if sound pressure is your goal and you have a solid state amp that can behave as a voltage source, a lower impedance will give you a little more output (not a lot; 3db more as the load impedance is halved) but the price paid is that the system becomes increasingly sensitive to the length and quality of the speaker cables.
So in general it can be said that speaker compatibility will be less critical if the speaker impedance is kept at a higher impedance; 8 or even 16 ohms.
Thanks for the comments anyway.
Why doesn't anyone seem to understand(you may just have written it poorly here) but SET is inherently class A. There can not be a class B SET amp.
"Why doesn't anyone seem to understand(you may just have written it poorly here) but SET is inherently class A. There can not be a class B SET amp. "
I, for one, don't understand. But then, I'm not an electronics guy. I'm a sound and acoustics guy. I know just enough about electronics to sometimes spot a good or a not-so-good electronics product, but I couldn't design either one. Only people who know about components and circuit design would understand. The average audiophile who doesn't work in audio only knows what they read in Stereophile or TAS (or on AA).
Ralph's post was very good - science oriented, not the typical "I like..." useless blather.
:)
And that's the problem. You need to know something about how things work and don't work. And the reviewers are like you; they often don't know. Other wise they wouldn't use redundant terms like SET class A or pure class where it's either class A or it isn't. Rich AB is good but it isn't class A. While how things work and measure may not be the whole story they often tell one a lot and are often warnings that what we hear is what we like but it may not be fidelity. In an imperfect world we need data and ears and the experience to use them together, a very rare commodity. A good example is Floyd Toole on speakers.
You mention Floyd Toole. I'll bring it back around to amplifier designers, since that's the topic at hand: John Curl, Charles Hansen, Nelson Pass, et al. These guys know the fundamental characteristics of components and topologies, and can design an amp six ways to Sunday based on the goals and price point. "Design the best damn amp you can!", versus, "Design the best damn amp we can sell for X thousand dollars!" Those are two different things, and even then, the more expensive amp doesn't mean it's the better amp. It'd be nice if they'd chime in to answer the OP's question.Channeling...
:)
Edits: 06/28/16
With regard to replying, John Curl said to me, "No. Why should I?" Ha!I swear, he's one of the most pragmatic people I've ever known. And, he's right.
What difference does it make? Most people have their preferences and/or biases set in stone, and no amount of talking/writing/discussing will change their mind.
:)
Edits: 07/01/16
51, Please don't project your personality on the rest of us. Some humans can respond to facts and evidence with change.
There is no audio Panacea, John , Pass , et al , know this better than most , if there were, everything would be class-A and be done already ..
My personal thinking is that the most attention should be paid to that first 0.1 to 2 watts output, since that's where a lot of systems are working most of the time. As an example, even though I can crank my lowly Dynaudio/Electro-Voice speakers to fill the house, most of the time I play them at a level where people can still talk at a normal conversational level, which means my stereo is basically slackin' it.The real problem with stereo systems, even after all these decades, is still the speakers. Can y'all say "10 percent harmonic distortion"? (Oops, there's another can o' worms!)
:)
Edits: 07/02/16
Agree on the 1st watt being important......
" is still the speakers. Can y'all say "10 percent harmonic distortion"? (Oops, there's another can o' worms!)"
Mostly low order and mostly in the bass where the hearing is far less sensitive. Probably makes the sound "fuller" than one without it.
With speakers it is still the problem with materials creating bending and breakup modes, storage and release of acoustic energy etc. rather than actual harmonic distortion from the driver non-linearities (they have gotten this part pretty good over the years).
Keep in mind that this kind of distortion is not the same type as generated by electronics, which have far more high order content in the distortion.
I once helped a friend by a stereo system. She (yes she) originally wanted a home theater but after we got a nice set of stereo speakers (AudioPlan Kontrast IIIi) she decided to have a good stereo instead. We auditioned many amps and some made the speakers sound truly and fundamentally different...not just a flavor change. The worst was the integrated Denon she already had...perhaps it was broken but the sound came out so flat, hard and aggressive as well as being stuck to the speakers that she was dumbfounded that it could sound so different. In the end she bought a SET (Cary CAD-572se monos) and a tube preamp (Transcendent Sound Grounded Grid, which I built for her) because that simply sounded far better with the same speaker and wires. She went from zero to SET cultist in one step!! She has very good ears (and brain) and it showed during her evaluations.
Distortion of the speaker itself didn't change but the distortion of the signal coming through it certainly did and it was easily (and sometimes painfully) audible. My guess is that the Denon probably measured just fine by objective standards (although I cannot confirm but it was probably 10 years old) but sounded like doodoo.
Quote :"" is still the speakers. Can y'all say "10 percent harmonic distortion"? (Oops, there's another can o' worms!)"
Mostly low order and mostly in the bass where the hearing is far less sensitive. Probably makes the sound "fuller" than one without it."
And that's why bass controls turnover at 100 Hz if you're lucky. They figure if you want more bass you want that tubby tone. Not me. Most rooms cancel out the lowest octave, it is that which needs to be boosted. What's more, a sealed cabinet is much better, even though it will inherently have less bass usually, the low end is not rolling off as fast.
The method of summing the output of the port and the woofer close miced does not give reliable results. They are not in phase. From what I have "heard" even the best of them suffer in a small room because to have to give them room to shake the air.
"With speakers it is still the problem with materials creating bending and breakup modes, storage and release of acoustic energy etc. rather than actual harmonic distortion from the driver non-linearities (they have gotten this part pretty good over the years). "
In other words, rattling. Just not rattling really bad right now. But you are right. Other distortion generated by the motor of the speaker should be pretty much gone now. In the old days they never expected the cone excursion of today. If they wanted bass they had to use a 15" woofer, some of the 8" of today can outdo them on low bass. And I do not mean one note resonant cavities, I mean something like a Boston Acoustics
A-70. And plenty others. I had the chance to audition a pair of Canton 10" three way system. I could not afford them at the time. The Bostons came closer than any other speaker I heard so I got those. Sealed system.Anyway, IIRC the Boston A-150s were 0.7 % THD at 1,000 Hz. Of course that is not the bass region but then any THD spec on a speaker is pretty rare. I do seem to remember that Quad ESL63s are rated very low in distortion and I mean less than alot of amps. I also wonder how the hell they measured it.
Edits: 07/14/16
Amplifier distortion can be measured but to hear it a set of speakers are needed, now you have a system, and the distortion of the system is strictly dependent on speaker distortion which usually are a several orders of magnitude higher than the amplifier.
Also, if you check out the specs of any high end speaker by checking manufacturers website you will notice that most specs exclude the lowest octave simply because those numbers are embarrassing.
Now back to Class A and the low distortion.
Vahe
I don't buy your argument vahe. I'm not sure I see the logic in it. One thing I do know is that millions and millions of audiophiles can hear that Class A sounds better. How do you come to the conclusion that because the speaker has more distortion that feeding it a signal with an increased or decreased distortion level cannot be perceived or isn't important? You are assuming that the level of distortion in the speaker is some kind of limiting factor. Tweaker
Edits: 07/05/16
"strictly dependent on speaker distortion which usually are a several orders of magnitude higher than the amplifier."
Maybe but the type of distortion and the distortion caused by the interaction of the amp and speaker are probably more detrimental to what you are hearing.
Surely you have had the experience of swapping out an amp on a pair of speakers and then it sounds almost like a completely different system? If you have then you are ignoring evidence that invalidates your comment above.
Or has every amp you have tried on a given set of speakers all sounded the same??
THAT is an excellent reply!
:)
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